"Did he use to work late" vs. "Has he ever worked late"

Question

My friend asked me the difference between these sentences:

1. Did he use to work in the office very late at night?

2. Has he ever worked in the office very late at night?

I told her:

• In #1, it means that I know the fact that he is working very late at present, and I want to know if he worked late in the past.
• In #2, it means that I don't know the fact he is working very late at present, and I want to know if he has worked very late once from the time he was born until now.

Did I explain them correctly?

Answer 1

The first sentence asks about something that happened regularly in the not just once. That is the difference to the second sentence. It is about an event that occurred only once.

Neither of the sentences imply if you know about him working late now.

Answer 2

It's simpler than that.

The first example is the present simple tense. We use the present simple to talk about events with a discrete beginning and end. Contrast that with the second example, which is present perfect. We use the tense in the second example to find out if it has happened or not. With present perfect we are not concerned with when, as is the case with the first example. In the second example we are concerned with if.

So you see you really asking two very different questions. The nature of these questions requires a different schema for ordering the past. I like to use particle physics as an analogy. The past simple considers the past as a particle. The present perfect considers the past as a fuzzy cloud of probabilities.